The present invention relates to controlled motion systems. Some aspects of the invention relate more specifically to controlled motion systems capable of independently controlling multiple movers on a track. The invention can be applied to controlled motion systems of the type disclosed in U.S. Pat. No. 6,876,107 issued Apr. 5, 2005 to Jacobs or U.S. Pat. No. 6,191,507 issued Feb. 20, 2001 to Peltier et al., both of which are incorporated herein fully by reference.
These prior art systems have several limitations that the present invention overcomes. One limitation is on nonlinear sections. On one type of prior art system, linear and nonlinear shaped sections are employed to create a path over which movers travel. This type of system uses “smart” sections which can independently control the motion of each mover on the section and “dumb” sections which drive each mover at the same speed. These dumb sections typically employ a rotary axis that drives movers with either a magnetic or mechanical coupling to the mover. A key problem with this prior art system is that in the transition zone from the “smart” to the “dumb” sections positive control of the mover is not maintained. This means it is possible for a mover to get stuck with no means of recovery other than operator intervention, which causes down time and lost production.
In another type of prior art system, a nonlinear or curvilinear shaped section is fabricated using a wedge-shaped, solid metal core, pole piece. This design suffers from large eddy currents leading to braking and loss of efficiency.
In another type of prior art system, a single-sided mover (magnets on only one side of a motor section), such as those taught in U.S. Pat. No. 6,191,507, is used. A key problem with these prior art single-sided movers is that they are not fully constrained against applied loads in any direction. Specifically, if a load greater than magnet preload is applied opposite the preload, the mover carriage will unseat. This prevents the track from being mounted in an arbitrary orientation or prevents the mover from being loaded with a load from an arbitrary direction because the mover might fall off the track.